Devices for determining the distance to objects are known. One currently used method is called “Time of Flight”. This method comprises sending a light signal towards the object and determining the time taken by the signal to travel to the object and back. The calculation of the time taken by the signal for this travel may be obtained by measuring the phase shift between the signal coming out of the light source and the signal reflected on the object and detected by a light sensor. Knowing this phase shift and the speed of light enables the determination of the distance to the object. Other techniques using histogram techniques are also known.
Single photon avalanche diodes (SPAD) may be used to sense the reflected light. In general an array of SPADs are provided as a sensor in order to detect a reflected light pulse. A photon may trigger an avalanche current in one or more of the SPADs in an SPAD array. The avalanche current may signal an event, namely that a photon of light has been detected.